In an air conditioning and heating system for vehicles it is a common practice to secure a heater core in a case such that the core covers an air flow passage. The core comprises a pair of spaced headers or tanks and a plurality of parallel flat heat exchange tubes connecting the headers. One known mounting arrangement utilizes two spring steel straps extending transverse to the tubes and screws at the ends for attaching the straps to the case. Thus six parts are used to hold the core to the case. During installation or subsequent servicing the six parts must be handled, one at a time. Also, during installation or servicing, a screw may be dropped in the case thus requiring a retrieval operation.